A non-emissive display produces information by varying the optical density on a display surface. One type of non-emissive displays is based on field-driven solid-phase particles. One class in such displays is the so-called electrophoretic display that is based on the principle of movement of charged particles in an electric field. In an electrophoretic display, the charged particles containing different reflective optical densities can be moved by an electric field to or away from the viewing side of the display, which produces a contrast in the optical density. Another class of the field-driven particles used in non-emissive displays includes the particles carrying an electric dipole. Each pole of the particle is associated with a different optical density (bi-chromatic). The electric dipole can be aligned by a pair of electrodes in two directions, which orient each of the two polar surfaces to the viewing direction. The different optical densities on the two halves of the particles thus produce a contrast in the optical densities.
The field-driven particles can be immersed in a fluid, which are together contained in a microencapsule. At each pixel of the display, an electric field can be applied to the solid-phase field-driven particles within the microencapsules by a pair of electrodes. The two electrodes can be spaced apart in a parallel fashion with the microencapsules sandwiched in between. In this case, the electrode on the viewing side is required to be transparent. The electrodes can also be both fabricated on the non-viewing side of the microencapsules.
One requirement for all displays using field-driven particles is to accurately place the field-driven particles and the associated microencapsules in registration to the electrodes. Furthermore, for color displays using the field-driven particles, it is essential to register the field-driven particles capable of displaying a specific color density and the associated microencapsules to the electrodes corresponding to the colors. Failure to do so will cause the display of incorrect color pixels.